1. Computers
  2. Display Drivers
  3. Graphics Cards
  4. Memory
  5. Motherboards
  6. Processors
  7. Software
  8. Storage
  9. Operating Systems


Facebook RSS Twitter Twitter Google Plus


Phoronix Test Suite

OpenBenchmarking.org

Intel Publishes New Linux P-State Driver

Intel

Published on 05 February 2013 02:10 PM EST
Written by Michael Larabel in Intel
2 Comments

Dirk Brandewie has published a new P-state driver for Intel Core CPUs on Linux. This new cpufreq performance state scaling driver initially is supporting just Sandy Bridge processors but will be expanded to handle other Intel hardware.

Intel's P-State Linux kernel driver is following a similar design to Transmeta's scaling driver. Here's the patch-set description from the kernel mailing list:
This driver implements a scaling driver with an internal governor for Intel Core processors. The driver follows the same model as the Transmeta scaling driver (longrun.c) and implements the setpolicy() instead of target(). Scaling drivers that implement setpolicy() are assmuned to implement internal governors by the cpufreq core. All the logic for selecting the current P state is contained within the driver no external governor is used by the cpufreq core.

At the moment only Intel SandyBridge processors are supported. As testing on SandyBridge+ processors is completed support will be added to the driver.

New sysfs files for controlling P state selection have been added to /sys/devices/system/cpu/intel_pstate/

max_perf_pct: limits the maximum P state that will be requested by the driver stated as a percentage of the avail performance.

min_perf_pct: limits the minimum P state that will be requested by the driver stated as a percentage of the avail performance.

no_turbo: limits the driver to selecting P states below the turbo frequency range.

The units for these for these files are purposely abstract and stated in terms of available performance and not frequency. In idea that frequency can be set to a single frequency is a fiction for Intel Core processors. Even if the scaling driver selects a single P state the actual frequency the processor will run at is selected by the processor.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
Latest Linux Hardware Reviews
  1. Intel Xeon E5-1680 v3 & E5-2687W v3 Compared To The Core i7 5960X On Linux
  2. Intel 120GB 530 Series SSD Linux Performance
  3. Btrfs/EXT4/XFS/F2FS RAID 0/1/5/6/10 Linux Benchmarks On Four SSDs
  4. AMD's Windows Catalyst Driver Remains Largely Faster Than Linux Drivers
Latest Linux Articles
  1. Mesa 10.5-devel Brings Some Intel Haswell HD Graphics Changes Over Mesa 10.3
  2. NVIDIA vs. Nouveau Drivers With Linux 3.18 + Mesa 10.4-devel
  3. Is The Open-Source NVIDIA Driver Fast Enough For Steam On Linux Gaming?
  4. Linux 3.18 File-System Performance Minimally Changed But Possible Regressions
Latest Linux News
  1. Amazon's Fire TV Stick: A Nice, Affordable Media Center Option
  2. Google Puts Chrome NPAPI Support On Final Countdown
  3. There's New In-Fighting Over The Future Of Compiz
  4. GTK+ Inspector Gains More Features Ahead Of GNOME 3.16
  5. Clang 3.6 Will Hopefully Have OpenMP Support
  6. A Go Front-End Could Soon Be Landing In LLVM
  7. Linux 3.18-rc6 Released, A Worrisome Regression Remains
  8. HandBrake 0.10 Brings H.265 & VP8 Encoders
  9. Gngr: A New Web Browser Focused On Privacy
  10. Linux 3.18 Kernel: Not Much Change With Intel Haswell Performance
Latest Forum Discussions
  1. Roadmap to Catalyst 14.10 ?
  2. how to configure module phoromatic ?
  3. PulseAudio 6.0 Is Coming & Other Linux Audio Plans For The Future
  4. Debian Developer Resigns From The Systemd Maintainership Team
  5. Updated and Optimized Ubuntu Free Graphics Drivers
  6. Cant get working Kaveri APU - A10-7850k
  7. Script for Fan Speed Control
  8. Debian Init System Coupling Vote Results